FINDING THE MAGNET POLES. 171 



The stone is to be made in globular form and polished 

 in the same way as are crystals and other stones. Thus 

 it is caused to conform in shape to the celestial sphere. 

 Now place upon it a needle or elongated piece of iron, 

 and draw a line in the direction of the length of the 

 needle, dividing the stone in two. Then put the needle 

 in another place on the stone, and draw another line in 

 the same way. This may be repeated with the needle in 

 other positions. All of the lines thus drawn "will run 

 together in two points, just as all the meridian circles of 

 the world rzm together in two opposite poles of the world." 



Here was a magnet made in spherical form, the poles 

 of it recognized and named, and the magnetic meridians 

 found. More than this, although the lodestone sphere 

 was regarded as an image of the celestial sphere, a certain 

 analogy between it and the terrestrial globe was also 

 plainly seen. Yet, again, more than three centuries were 

 to intervene before William Gilbert should perceive in 

 the globular magnet of Peregrinus a miniature earth, or, 

 in the world itself, only a great magnet a colossal re- 

 production of the Pilgrim's lodestone ball. 



Peregrinus probably first found the poles in the way that 

 is above described. Then afterwards he remarked that, at 

 the points so determined, the needle was more strongly 

 attracted than elsewhere. Consequently, he sees that the 

 poles can be detected without marking the meridians, by 

 simply noting the places on the stone where the needle is 

 most frequently and powerfully drawn. If, however, he 

 continues, you wish to be precise, break the needle so as 

 to get a short piece, about two nails in length. Place this 

 on the supposed polar point. If the needle stands perpen- 

 dicularly to the surface of the stone, such point is the true 

 pole ; if not, then move the needle about until the place is 

 found where it does thus stand erect. If these points are 

 accurately ascertained and the stone is homogeneous and 

 well chosen, he adds, u they will be drawn diametrically 

 opposite one another like the poles of the sphere. n 



